The Function Graphed Is of the Form Y $$y = a \sin b x \text { or } y = a \cos b x , \text { where } b > 0$$

The function graphed is of the form y $$y = a \sin b x \text { or } y = a \cos b x , \text { where } b > 0$$ Determine the equation of the graph.
-A weight attached to a spring is pulled down 7 inches below the equilibrium position. Assuming that the period of the system is $\frac { 1 } { 5 }$ second, determine a trigonometric model that gives the position of the weight at time $t$ seconds.

A) $y = 7 \cos 10 \pi t$
B) $y = 7 \cos \frac { 1 } { 5 } t$
C) $y = - 7 \cos 10 \pi t$
D) $y = - 7 \cos 5 \pi t$